Internal combustion engine



FIG. 1 is a front view of an internal combustion engine in accordance with the present design;

FIG. 2 is a rear view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a front perspective view thereof; and,

FIG. 8 is a rear perspective view thereof.

The portions of the engine shown in broken lines form no part of the claimed design. 

The ornamental design for an internal combustion engine, as shown and described. 